Forge Worlds are planets of the Adeptus Mechanicus, devoted entirely to industry and the worship of the Cult Mechanicus. The majority of a Forge World's surface is built up of massive industrial complexes, great machine factories, production centres and other facilities dedicated to the construction, maintenance and production of the Imperium's war machines. They are also home to the immense Titan Legions.

The Forge World Graia in particular can be characterized by its work on the Graia Pattern Hellhound.